Process and apparatus for exterminating pests in articles



T. wEHRLE 2,119,837

PROCESS AND APPARATUS FOR EXTERMINATING PES'ISv IN ARTICLES June 7, 193s.

Filed March 21, 1935 2 sheets-'sheet 1 T. WEHRL y2,119,837 PRocEss AND APPARATUSFOR EXTERMINATING PEsTs 1N ARTICLES Jne 7, 1938.

Filed Mam 21, 1935 2 sheets-sheet 2 MII Theodor WeZajZe,

Patented June 7, 1938 UNITED STATE-sA PROCESS AND APPARATUS FOR EXTER- MINATING PESTS IN ARTICLES Theodor Wehrle, Basel, Switzerland, assignor to the' firm Deutsche Gesellschaft fr Schdlingsbekmpfung m. b.

H., Frankfort-on-the- Main, Germany, a corporation of Germany Applicata@ March 21, 1935, serial No, 12,313

-In Switzerland March 28, 1934 14 Claims.

The process according to this invention for` exterminating pests by circulating a gas, for

example lair, with the aid of a compressionmump through a poison gas generator or space in which the gas is charged with the toxic substances and thence through a fumigating chamber containing the material to be treated, preferably in a state of rest, is characterized by the fact that considerably reduced pressure and that a. constrictionus introduced into the passage of the gas prior to its entry into thefumigating space, so that during each cycle the gas is compressed prior to its discharge into the fumigating space ,and acts in this compressed condition on the toxic substance, which may ifdesired be associated with a carrier, after which the gas is allowed to expandbefore its entry into the fumigating space, the gas being compressed to such a considerable extent that the fall of temperature caused by the vaporization of the toxic substance is entirely or substantially equalized by the increase in temperature of the gas produced by the compression.

My invention is illustrated by way of example in the accompanying drawings, in which:

Fig. l shows in perspective, partly in section, one form of apparatus suitable for carrying out the process of my invention.

Fig. 2 is a similar view of a modified form.

Referring to Fig. l of the drawings, the fumigating chamberu is connected by the pipe lead b with a pump c and the latter by the pipe lead d, by Iway of the valve lc with the inner chamber of the poison gas generator e and the latter byi the lead f b-y way of the throttle valve g with the fumigating chamber a. The waste gas from the pump c may be fed by Way of the valve k, poison gas generator e and valve g into the chamber a, or may discharge through the valve s into the atmosphere or may be introduced the fumigating chamber or space stands under 1 from the jacket through valve z' into the atmosphere. t is a stop valve discharging into the atmosphere., p Y

A combustion engine g drives the pump c through a driving wheel` r, a belt u and a driven 5 wheel v. The exhaust pipe w of the engine q is provided with a valve :c permitting direct ejection of the exhaust gases into the air, and a branch pipe a which, in turn, is provided with a valve y and connected to pipe d. If valve :c is 10 closed andvalve y opened, the hot exhaustigases of the engine q are injected into pipe d and therefore into the poison gas cycle for acting therein as a-carrier for the poison gas and for heating the contents of the gas generator e.

The process is carried out with the aid 0f the above described apparatus somewhat as follows:

After introducing the article or material to be treated into the chamber a the main quantity of -the air in the chamber a is sucked out with the aid of the pump c whilst the valve g is closed and the valve m opened and is removed from the system fori'example through the valve s.. After the desired quantity of air has been removed, the air outlet valve s is closed andthe valves 9 25 and k are opened, after which the air still remaining in the chamber is circulated through the poison gas generator e and the chamber a, whereby it becomes charged in the generator e. with poison gas, for instance hydrocyanic acid, ethylene oxide or the like, after which it is introduced through the lead j into the chamber a and again passed `back to the pump throughv the lead b. The throttle valve g disposed in advance of the inlet position of the poison gas mixture into theI chamber should be so adjusted that compression of the air in the system d, e, and f takes place to such a degree that the air flowing through thegas generator owing to the heat of compression acquires a marked increase` 4o in temperature which promotes the vaporization of the toxic substance in the poison gas gener- .l ator and is sufficient entirely or at least to a considerable extent to equalize the fall of temperature caused'by the vaporization of the toxic 45 substance.

Instead of, or in addition to, a regulable valve g or other closing member, such as a slide valve, throttle valve and the like, a non-regulable device for throttling the passage of gas, for exam- 'ple in theform of a nozzle or other constriction may according to my invention be provided in the connecting lead between the pressure side of the pump c and the chamber a. A

It is advisable when evacuating the chamber 10 substance or toxic substance carrier in the generator. This effect may be still further increased by compressing the air by throttling the same after its passage through the heating jacket. of

the generator, for example with the aid of the i 15 air discharge'valbve i.

Heating the circulated gas by compressing the same before its entry into the fumigating space oiers various important advantages. In the iirst place it offers the advantage of an increase in 20 the bactericidal and insectlcidal action of the Heatingheated gas in the fumigating chamber. the gas has also the further advantage that less of the heated gas is retained in and on the fumigated articles than of the cold gas.

l' 25 A particularly important advantage of compressing the poison gas mixture before its entry into the fumigating chamber resides in the fact that on passing the gas through the poison gas generator not only is the quantity of toxic sub- 30 stance carried along with the air or other carrier gas in unit of time considerably increased, but

also such eiiicient heating of the toxic substanceor toxic substanceycarrier is effected in the generator that the operation can vb'e carried out at. 35 greater speeds than in the known processes without the danger of a liquid toxic substance congealing owing to the fallin temperature produced by evaporation. 1 L Itis therefore possible by operating according 40 to -my invention to accelerate the fumigating process to an extraordinary degree.

'Ihis 'favourable effect may, as already mentioned, be still further increased by. passing the air, which discharges from the pressure side of 45 the pump on c vacuating the chamber a and has with advantage been' compressed by throttling, before its discharge into the atmosphere, through a heating jacket surrounding the poison gas generator or by utilizing this air in another manner l '50 for the indirect heating of the contents of the a ator with poison gas, enters the cycle of the working gas in place of, or in addition to, the air or the like otherwise introduced.

The action of the poison` gas mixture or the toxic substance at increased pressure is adapted a5 substantially to accelerate the vaporization of the toxicsubstance.

'I'he gas charged with toxic substance can be circulated in the manner described continuously or interruptedly through the poison gas generator and the fumigating chamber until, if necessary after repeated circulation, it is charged with the desired quan ity of poison gas. The circulation may then for example be interrupted and the poison gas be allowed to'react in a state of rest 75 4on Ithe articles' undergoing fumigation in the chamber until the desired effect is obtained. An alternative procedure is to eifect further continuous or intermittent circulation of the air charged with poison gas through the fumigatingchamber,

with or without compression until the desired ef- 5 fect is obtained, the poison gas generator being if necessary permanently or temporarily cut out of the circuit. i

'I'he poison gas maybe evolved in the generator; for example from' liquids which are capable of i0 being absorbed by porous substances. For the evolution of hydrocyanic acid gas, liquid hydrocyanic acid, if desired absorbed on kieselguhr or the like, may for example be employed. The generator may be charged with quantities of products capable of yielding the poison gas, which have been'l found by experience to be just suiilcientfor one fumigating treatment or with greater quantities. Instead of subjecting the toxic substance or the carrier charged with toxic substance in a separate generator to the action of the carrier gas, it may also be introduced into the gas stream at any point of the gas passage between the pump and fumigating'chaniber, for example y by spraying in liquid hydrocyanic acid.

According to one embodiment of the invention the introduction of the toxic substance or the carrier charged with toxic substance into the gasl stream in advance of and/or within the fumigating chamber may be eiected by producing the desired compression and heating of the gas entirely or partially by the resistance'oiered to the passage of the gas by the toxic substance or toxic substance carrier introduced into the gas passage for example in granular to iinely fragmentary form, if desired in combination with a 'throttling action exerted at another point of the gas passage.

Thus, for example, the toxic substance or toxic l substance carrier may be disposed in the poison`40 gas generator e of the drawings in a layer of such length and depth that it oifers the requisite resistance to the gas flowing therethrough.

The pressure in the lfum gating chamber is maintained considerablybelow atmospheric pressure during the fumigating process, whilst the pressure in the. passage of the gas between the pressure side of the pump and the fumigating chamber or inthe poison gas generator is higher than the pressure in the fumigating chamber. The pressure between the pump and the fumigating chamber may' be below, at, or in certain cases also above atmospheric pressure. Because of the considerable reduction of pressure in the fumigating chamber, the penetrationv of' the poi- 55 son gas into the hollow spaces, clefts and pores of the articles orbmaterials undergoing treatment is promoted. Th action is further increased and rendered uniform by the circulation. Care must be taken by'suitable disposition of the inlet and 60 discharge positions of the gas and suitable charging of the chamber to ensure that the poison gas contacts as simultaneously as possible with all the parts of the articles under treatment.

Afterthe extermination of the pests the poi- 05 son gas is removed from the fumigating chamber, for example by suction followed if necessary by flushing through with fresh air, after which the chamber is emptied and can be charged afresh.

According to a furtherfeature of this invention, the gas still containing toxic substance on its removal from the chamber a. can be introduced by way of the lead o and whilst valves s, k and'm are closed and valve n is opened under pressure into a reservoir p and be subsequently again after being three times aerated, still contained introduced, after charging the chamber with fresh material, back through valve n and lead o or in another way into the chamber a or into a. fresh gas cycle. The poison gas `generator may also itself be constructed in the form of a reservoir by imparting the requisite dimensions thereto.

It is advantageous after completion of the fumigating process and before evacuating the chamber to allow a little air to enter into the chamber for example through the valve t, whereby the gas still left in the chamber and still containing toxic substance is forced into the pores of the fumigated articles and can thereby exert any desired subsequent action.

The aeration of the chamber a before removing the fumigated articles therefrom is with advantage effected as follows: v

The chamber is first extensively evacuated whereby the greater portion of the poison Agas adhering to the previously fumigatedarticles is removed. Fresh air is then sucked by opening the closing member t into the chamber, which air owing to the high vacuum in the chamber penetrates into all the pores of the articles and becomes mixed by diffusion with any residual gas which may be left in the chamber in a concentration still detrimental to health. Gas is then again sucked out of the chamber with the aid of the pump c and the sucked out mixture of air and toxic substance in the form of gasV or vapour is allowed to escape into the atmosphere either directly through valve s or through a device (not illustrated-in the drawings) adapted for the recovery of the residual quantities ofi toxic substance still contained in the gas. This aeration process is with advantage several times repeated, in order to allow the chamber to be entered without danger with a view to emptying the same and introducing -a fresh charge. Experiments have shown that with an original content of about 20 gms. of hydrocyanic acid per cubic meter inf.r the working gas, a chamber,

only 1.5 mgms. of hydrocyanic acid, in any case ,however less than th'e smallest quantity capable of being analyticallyaccurately' determined (10 mgms. of hydrocyanic acid per cubicmeter).

Experience has shown it to be possible to endure Y a quantity of hydrocyanic acid amounting to 50 mgms," per cubic meter of air without danger to y health.

Two or more fumigating chambers may also be employed for carrying out my' hereinbefor'e described process. 'I'heir employment offers the vadvantage that the greater portion of the re- Y sidual poison gas mixture remaining in the fumiyoperated fumigating chambers; 3 is a vacuum pump, 6 a poison gas generator and 1 a device for ascertaining the toxic substance content of the gas. The aforementioned parts are connected together in the manner shown in the drawings.

8-20 are closing members which are with ad- .vantage capable of control.

At the conclusion of a fumigating-process in chamber I, chamber 2, which has been previously charged with other articles to be fumigated, is extensively evacuated with the aid of the vacuum pump 3, for example until a pressure of about 20mm. of mercury is reached, for which purpose the closing membersl 9, II,-and I3 are opened, y whilst the remaining closing members at first' remain closed. By closing the closing member 9 and opening the member 8, the working gas is then allowed to expand from chamber I into chamber 2, until the pressure is equalized. The

residual gas still present in the chamber I is then conveyed with the aid of the pump 3 withr open closing members 8, 9, and Ill and closed members I-I, I2, I3, I1, and 20 through the open closing member I8 into the chamber 2 until a high vacuum is produced in chamber I for the next fumigating process to be effected therein and an excess pressure for example from 30G-400 mms. of mercury is present in chamber -2.

The gas is then circulated byfpump 3 with closed closing member I2 in the above described manner during .the whole or a part of the fumigating process through the open closing members II and. 8 with closed members 8, I8, I3, I5, I8, and 20 through the open closing members I1 and I6` and the fumigating chamber 2, care being with advantage taken to ensure sufficient compression and heating of the gas by throttling the gas passage, forfiexample at the closing member I6. During this gas circulation or even only during a part thereof, for example until suiiicientpoison gas concentration in the' working gas has been obtained, poison gas or vapour is introduced from the generator 6 through the open member I4 into the stream of working gas. Analternative procedure is entirely to interrupt the circu-- lation after sumcient poison gas concentration has been obtained and 'to cause-the gas to react in a state of rest on .the articles introduced into the chamber.

Samples of the streaming gas can be removed at every stage of the operation with the aid of the apparatus 1 lbranched off from the circuit, a fact which is of importance, particularly during the aeration of the chambers, for the exact determinationof the toxic substance still present in the gas., 'Ihe circulation of the. working gas through the chambers and with advantagealso the transference of the residual gas of anished fumigation into another chamber is with par` ticular advantage effected at least during a part of the fumigating process through the poison gas i generator and uthe closing members 28 and Il with closed members 8, I0; I2, I3, I1, I8, and I9,

vwhereby particularly abundant quantities of the toxic substance can be taken up by the gas in direct contact with vthe toxic substance or carrier of thesame and the heat produced in the gas by compression for example by the member I6 be utilized directly for the vaporization of the toxic substance in the generator.v f

After completion of the fumigation-in chambei` 2 this chamber, after chamber I has been charged with freshmaterial to be'fumigated, can be emptied whilst repeating the above described procedure in a reverse direction and a fresh fumigation be carried out in chamber I.

l, In the case of the above described embodiment the poison gas generator may also be provided with a heating jacket for heating, for example with the aid of the exhaust gas of the motor driv` into another chamber, for example by transfer ring the heat of the discharging poison gas mixture by means of a heat exchange apparatus not shown in the drawings) indirectly to the poison gas mixture flowing into the other chamber.

When operating with two chambers and also when operating with only one chamber, a reservoir corresponding to the position p in Fig. 1 mayD be provided for storing the working gas under pressure, for example in the event of one chamber being o'ut of action or the necessity at any time of makingboth chambers simultaneously available. Y

In place of two chambers several chambers may be connected together in a manner correspending to the above described procedure, the

gas residue of each fumigation being utilized in members I9, I4 and i5 or I6 through the poison gas generator into the chamber to be aerated.

When employing more than one fumigating chamber each chamber may be all^tted a separate poison .gas generator with corresponding modification of the circuit.

Example 'I'hrough a chamber a of 20 cubic meters capacity filled with the articles to be fumigated, after evacuation has been effected with the aid of the suction andpressure pump c to a pressure of 160 mm. of mercury, the compressed waste gas ofthe pump having beenA passed through the jacket h of the poison gas generator e in order to pre-heat the contents thereof, consisting of 500 gms. of hydrocyanic acid absorbed in 1000 gms. of kieselguhr or diatomite, the residual gas is circulated for 8-10 minutes through the generatonwhereby the gas pressure in the chamber amounted to mm. of mercury and the gas pressure between the pump and -the throttling position be'- hind the poison gas generatoramounted to 1 atm. After removing the air still-'charged with hydrocyanic acid present in the chamber after the time indicated with the pump c or afterpassing the residual gas back into another chamber and ushing the evacuated chamber in the manner described, this chamber may be opened and emptied.

If desired before mptying the chamber the gas. first circulated through'the poison gas generator and the chamber, can be circulated through thel chamber for a further period whilst cutting the poison gas generator out of the circuit and/or without effecting throttling between the pump and the chamber.

InA order to increase the final action of the poison gas in the chamber some air may be allowed to ilow in from outside before emptying the chamber until the gas pressure in the chamber amounts to about 360 mm. of mercury.

What I claim is:

1. A pest-exterminating process.. which con-l sists in circulating gas through a space in which the gas is charged with a volatile toxic substance and thence through a fumigating chamber containing the material to be treated,v the fumigating chamber standing under considerably reducedA pressure, during each cycle compressing the gas prior to its discharge into the fumigating chamber so that the gas acts in this compressed condition on the toxic substance, and allowing'the gas to expand befor'e its entry into the fumigating chamber, the gas being compressed to such a considerable extent that the fall of temperature,

caused by the vaporization of the toxic substance vber is sucked out of the latter after charging the fumigating chamber with the articles to be treated and then the air remaining in the chamber is circulated through the latter and the space charged with the toxic substance, compressing the air rst sucked out before-its discharge *o the atmosphere, and indirectly transferring the resulting heat of compression to the toxic substance to be vaporized.

4. A process as claimed in claim 1 wherein the circulation is eifected by means of a. compression pump driven by a combustion engine, the hot exhaust gas of the latter being at least partially employed as circulating carrier gas.

5. Apparatus for exterminating pests, which consists of at least one chamber to be charged with the articles containing the pests, a container for a substance giving oir a volatile toxic substance inserted in the gas stream, a pump adapted for use both as a suction pump and a pressure pump, connecting leads and closing and reversing members for circulating a gas through the pump, the i'umigating chamber andthe said container. and means for throttling the ow -oi' gas between thepoint of discharge fromsaid container andthe point of entry into the fumigating chamber. so that the-fall of temperature y caused by the vaporization of the toxic substance is at least in a great measure equalized by the increase in temperature of the gas produced'by the compression.

6. Apparatus as claimed in claim 5, wherein the throttling means are adapted to regulate the resistance to the passage of the gas.

7. A process as claimed inclaim 1, wherein air is employed ascarrier gas for the toxic substance.

8. A 'process as claimed in claim 1, wherein the gas is charged with the toxic substance by causing the gas stream at least during a part of its circulating period to contact directly with a solid carrier charged with a volatile toxic sub-v I stance introduced into the gas cycle so that it gas still containing toxic substance present in the 4 fumigating chamber is transferred into another chamber which has been previously extensively 70 evacuated and charged with the articles to be treatedA and is there employed for carrying put a fresh fumigating process.

11. Apparatus as claimed in claim 5. wherein a substance charged with the toxic substance o sure side in order to increase the resistance to the passage of the gas, a separate toxic substance container being dispensed with.

12. Apparatus as clalmedin claim 5. wherein members for introducing the exhaust gas of the internal combustion engine driving the pump are provided in the gas cycle at a point in front of the point of introduction of the toxic substance into the same.

13. Apparatus as claimed inclaim;;5, wherein,

when employing at least two fumigating cham. bers, members are provided for transferring they residual gas remaining in one chamber after completion of fumigation into another chamber and for eiecting the, circulation of gas through this chamber.

14. A process as claimed in claim 1, wherein.

ethylene oxide is employed as toxic substance to be admixed in vapourized iorm with the gas.

` THEODOR WEHRLE. 

